After you complete ALL 2015 paychecks, you can download the latest version ezAccounting software and purchase the new key at

http://accounting.halfpricesoft.com/accounting-software-download.asp

ezAccounting 2016 installation package will update tax rate. You should run it after you completed ALL the paychecks for Year 2015. With ezAccounting 2016, you can still access your 2015 paychecks, view reports and print 2015 W2 forms.